This invention relates to apparatus of the type disclosed in U.S. Pat. No. 3,466,808 for reconditioning by finishing and "trueing" large diameter, loadbearing circular supports such as the kiln rings, or "tires," which are affixed to and rotatably support rotary kilns and driers used principally in the manufacture of cement.
Tubular rotary kilns commonly of three to four hundred feet in length and ten to twenty or more feet in diameter are used in the manufacture of cement and pulverized lime from limestone and clay. Such long rotary kilns are relatively flexible and have kiln rings, or riding rings affixed thereto of hardened steel machined to close tolerances and several inches thick and several feet in axial length disposed about the periphery of the kiln at spaced distances of forty to sixty feet, for example. The kiln rings are supported and rotate on trunnion roller mountings. Such relatively flexible kilns are heated to high temperatures and continuously rotated over long periods of time and do not necessarily rotate about a fixed central axis since over extended periods of use the kiln rings wear irregularly and may exhibit excessive wear which appears as pitting of the surfaces of the kiln rings or as a deviation of the axial surface from flatness. Replacement of the kiln rings necessitates shutting down the kiln for several weeks with the resulting expensive loss of use of the kiln in addition to the high cost of replacing the kiln rings. In order to avoid deterioration of the kiln rings to the point that they and the trunnion rollers must be replaced, it is common practice to grind the surfaces of the kiln rings until their axial profile is again flat.
Such grinding takes place wile th kiln is in operation and rotating. Both grinding wheels, such as disclosed in U.S. Pat. No. 3,466,808, and grinding belts have been used to recondition the kiln rings. The grinder of prior art apparatus typically was rigidly mounted on a stationary support near the kiln. Usually the kiln ring surface will not follow a uniformly circular path with respect to the stationary grinder. In one instance the kiln ring may wear into an oval profile; in another, the kiln ring may undergo translation movement off of and back onto its supporting trunnion rollers; and in still another, the kiln ring may exhibit large surface profile changes such as bumps, grooves, cavities and flat spots.
In order to maintain uniform grinding, the grinder must be capable of translational movement in a direction radial of the kiln ring to follow changes in the path of the kiln ring surface. Non-uniform grinding could change the circumferential profile of the kiln ring, whereas the grinding is only intended to flatten the axial profile of the ring. Further, inability of the grinder to be translated in a direction radial of the ring in compliance with the surface of the ring could create excessive forces between kiln ring and grinder which might damage ring and/or grinder.
In order to assure compliance of the grinder to the kiln ring surface, it is known in the prior art to use springs to urge the grinder toward the kiln ring. Further, aforementioned U.S. Pat. No. 3,466,898 discloses a combination of mechanical support points on the kiln ring itself together with means permitting limited movement of the grinder relative to the kiln ring while the weight of the grinder is exerted on the kiln ring for the purpose of assuring compliance of the grinder to the kiln ring surface. In such prior art apparatus, control of grinding uniformity is maintained by manual adjustments to the grinder supports to hold a constant grinding pressure.